1. Field of the Invention
The invention relates to a switchover valve unit for an internal combustion engine with an adjustable compression ratio, and to an internal combustion engine.
2. Description of the Related Art
DE 10 2010 016 037 A1 and FIG. 1 herein show a connecting rod 10 of an internal combustion engine with an adjustable compression ratio. More particularly, the connecting rod 10 shown in FIG. 1 has a crankpin bearing eye 11 and a connecting rod bearing eye 12. The crankpin bearing eye 11 is used connects the connecting rod 10 to a crankshaft (not shown in FIG. 1), and the connecting rod bearing eye 12 connects the connecting rod 10 to a cylinder piston (not shown in FIG. 1) of the internal combustion engine. The connecting rod 10 is assigned an eccentric adjustment device 13 that has an eccentric body 14 and eccentric rods 15, 16. The eccentric body 14 has a piston pin bore that is arranged eccentrically with respect to a central point 17 of the connecting rod bearing eye 12, with a central point 18. The piston pin bore receives a piston pin. The eccentric adjustment device 13 is used to adjust an effective connecting rod length Ieff. The connecting rod length is understood as the distance between the central point 18 of the piston pin bore and a central point 19 of the crankpin bearing eye 11. The eccentric rods 15, 16 of the eccentric adjustment device 13 are displaceable to rotate the eccentric body 14 and thus to change the effective connecting rod length Ieff. Each eccentric rod 15 is assigned a piston 20 and 21 that is mounted or guided displaceably in a hydraulic chamber 22 and 23.
Hydraulic pressure in the hydraulic chambers 22, 23 acts on the pistons 20 and 21 respectively assigned to the eccentric rods 15, 16. The displacement of the eccentric rods 15, 16 is possible or is not possible in a manner dependent on the amount of oil in the hydraulic chambers 22, 23.
The adjustment of the eccentric adjustment device 13 is initiated by action of mass and load forces of the internal combustion engine that act on the eccentric adjustment device 13 during a working stroke of the internal combustion engine. During a working stroke, the directions of action of the forces acting on the eccentric adjustment device 13 change continuously. The adjustment movement is assisted by the pistons 20, 21. The pistons 20, 21 are acted on by hydraulic oil and act on the eccentric rods 15, 16. Thus, the pistons 20, 21 prevent a return movement of the eccentric adjustment device 13 due to varying directions of force action of the forces acting on the eccentric adjustment device 13. The eccentric rods 15, 16 that interact with the pistons 20, 21 are connected to the eccentric body 14 on both sides. The hydraulic chambers 22 and 23 in which the pistons 20 and 21 are guided can be charged or filled with hydraulic oil from the crankpin bearing eye 11 via hydraulic oil feed lines 24 and 25. Check valves 26 and 27 prevent a backflow of the hydraulic oil from the hydraulic chambers back into the hydraulic oil feed lines 24 and 25. A switchover valve 29 is accommodated in a bore 28 of the connecting rod 10. The hydraulic chambers 22 and 23 are in contact, via hydraulic oil discharge lines 30 and 31 respectively, with the bore 28 that accommodates the switchover valve 29. The switching position of the switchover valve 29 determines which of the hydraulic chambers 22 and 23 is filled with hydraulic oil and which of the hydraulic chambers 22 and 23 is evacuated. Thus, the adjustment direction or direction of rotation of the eccentric adjustment device 13 is dependent on this.
The switchover valve 29 of DE 10 2010 016 037 A1 comprises an actuating element 32, a restoring spring 33 and a control piston 34.
As stated, the pistons 20, 21 of the eccentric rods 15, 16 are guided in the hydraulic chambers 22, 23, and the hydraulic oil that acts on the pistons 20, 21 is supplied to the hydraulic chambers 22, 23 from the crankpin bearing eye 11 via the hydraulic oil feed lines 24 and 25. The connecting rod 10 engages by way of the crankpin bearing eye 11 on the crankshaft (not shown in FIG. 1) such that a connecting rod bearing shell 35 is arranged between the crankshaft, specifically a crankshaft bearing journal thereof, and the crankpin bearing eye 11.
The hydraulic chambers 22, 23 can be ventilated in a manner dependent on the switching position of the switchover valve 29, via the hydraulic oil discharge lines 30, 31. The adjustment direction or direction of rotation of the eccentric adjustment device 13 is dependent on this.
The switchover valve 29 of DE 10 2010 016 037 A enables the adjustment direction or direction of rotation of the eccentric adjustment device to be influenced in an effective manner. However, there is a demand for a switchover valve that can be manufactured and assembled more easily.
It is an object of the invention to provide a novel switchover valve unit for an internal combustion engine with an adjustable compression ratio, and an internal combustion engine having such a switchover valve unit.